In recent years, portable terminals have been widely used because they can be easily carried and provide a variety of functions including a voice call function. Portable terminals are now serving as multimedia communication systems because they can provide data transmissions services and other various additional services.
Portable terminals each include a processor for executing a general application and circuitry for driving the processor. The circuitry includes an inverter for inverting an input signal. The inverter is connected with a feedback resistor for stabilizing a circuit. When the inverter feeds its output back to the input terminal, a direct current (DC) bias voltage is derived to the line connected to the feedback resistor. The DC bias voltage increases the magnitude of the voltage output from the inverter. This causes the portable terminal to increase the power consumption. In particular, this phenomenon increases the power consumption of the battery even when the portable terminal is operating in sleep mode, thereby causing the rapid depletion of the battery power.